High voltage supplies may be used in different applications. In some of these applications, rapid changes to one or both of current and voltage may be needed. For example, x-ray tubes (having high voltage supplies) may be used in a variety of applications to scan objects and reconstruct one or more images of the object. In computed tomography (CT) imaging systems, an x-ray source, such as an x-ray tube, emits a fan-shaped beam or a cone-shaped beam toward a subject or an object, such as a patient or a piece of luggage, which is then detected by a detector array. In particular, in CT systems, the x-ray source and the detector array are rotated about a gantry within an imaging plane and around the subject.
Furthermore, the x-ray tube may include, for example, an emitter from which an electron beam is emitted toward a target. The emitter may be configured as a cathode and the target as an anode, with the target at a substantially higher positive voltage than the emitter. Electrons from the emitter may be formed into a beam and directed or focused by electrodes and/or magnets. In response to the electron beam impinging the target, the target emits x-rays. The emitter may contain a number of electrodes used to set the local electric field on the emitting structure.
The voltage supplied to the electrodes of the emitter may be controlled to adjust the intensity or energy of x-rays that are generated. In some of these systems, with respect to controlling the emitter, it is desirable to be able to produce fast transitions from low to high voltages, and vice versa, which may require fast current measurements.
Conventional control systems and methods, particularly that include arrangements for measuring the tube current, measure the cable charge current, which may be difficult or inconvenient to perform. Some systems use insulated measurement devices at the high-voltage potential, but do not have a shield at the high-voltage potential that connects to the x-ray tube. Other approaches add components to the x-ray tube that can add cost, complexity or failure modes.